co=coroutine.create(function()
 print("hi")
end)
print(coroutine.status(co))
coroutine.resume(co)
print(coroutine.status(co))
print()

co=coroutine.create(function()
 for i=1,2 do
 print("co",i)
 coroutine.yield()
 end
end)
coroutine.resume(co)
print(coroutine.status(co))

coroutine.resume(co)
print(coroutine.status(co))

coroutine.resume(co)  --没有输出
print(coroutine.status(co))
print()

co=coroutine.create(function(a,b,c)
 print("co",a,b,c)
end)
coroutine.resume(co,1,2,3)

co=coroutine.create(function(a,b)
 print("I'm before yield")  --第一次运行执行
 coroutine.yield(a+b,a-b,"needless args")  --在这停住,返回yield的参数
 print("Mgs")
end)
print(coroutine.resume(co,20,10)) --参数传给yield,处理后再返回
print("I print first")
coroutine.resume(co)

co=coroutine.create(function()
 return "I'll return"
end)
print(coroutine.resume(co)) --主函数的返回值回传给resume
print()

suspended
hi
dead

co 1
suspended
co 2
suspended
dead

co 1 2 3
I'm before yield
true 30 10 needless args
I print first
Mgs
true I'll return